As integrated circuit (IC) geometries continue to decrease, and with the advent of Micro-Electro Mechanical Systems (MEMS), the need for reliable, high density packaging solutions increases. A promising solution for providing reliable packaging for chips of continually decreasing size is Wafer Level Packaging (WLP). WLP is a packaging method in which packaging is formed at the wafer level in an IC foundry or other processing location, allowing testing and burn-in to be performed before the dicing of individual chips.
In certain wafer level packaging (WLP) methods, small cavities or enclosures of an IC or MEMS package may be filled with fluid. In many such applications, fluid filling in a WLP may need to be performed in such a way as to prevent bubbles or gaseous pockets from forming in the fluid filled cavities.
Fluid packaging may perform a number of functions essential for an IC or MEMS device. Packaging may provide electrical connection, electrical isolation, or passivation from moisture and electrolytes, physical isolation from the environment to provide structural integrity of mechanical devices, thermal and optical protection to prevent undesirable performance changes, and chemical isolation to protect from harsh chemical environments. Electrical connection and isolation may include providing electrical connections from the outside of the MEMS package to electrical or mechanical components of the MEMS device inside the package, electrostatic shielding of the MEMS device, and preventing penetration of moisture and subsequent corrosion of electrical components or undesired interface adhesion.
The fluid is often introduced to the MEMS package by way of a fill port. In order to maximize the protections previously described, the fill ports may be sealed. The process of sealing the fill port is subject to many different variables that can occur during processing. These variables include temperature drift, time at temperature, and fluid properties such as viscosity. These process variations may cause the adhesive to be drawn into the MEMS packaging and onto the MEMS device itself. The presence of adhesive on the MEMS may render the MEMS device inoperable.